High energy forming

ABSTRACT

The invention relates to the forming of articles such as collapsible tubes and bottle closures. The article is inserted in a forming chamber having a die surface and a combustible gaseous mixture is ignited. The products of combustion result in increased pressure within the forming chamber to produce expansion of the article against the die surface.

United States Patent 1 Brownbill 1 Sept. 30, 1975 1 1 HIGH ENERGY FORMING [75] inventor: Thomas Duncan Brownbill, London,

England 22 Filed: Nov. 13,1973

211 Appl.No.:4l5,37l

3,228,222 1/1966 Maier 72/56 3,236,080 2/1966 lllgen v 72/56 3,252,312 5/1966 Maier 72/56 $342,048 9/1967 Johnson et 31.... 72/56 3.475.229 10/1969 Geen et al. 72/56 3.712.022 1/1973 Erlandson 72/56 Primary ExaminerRichard J. Herbst Attorney, Agent, or FirmEdwin E. Greigg Foreign Application Priority Data ABSTRACT Nov. 17. 1972 United Kingdom 53264/72 Feb. 20, 1973 United Kingdom ()8359/73 The invention relates to the forming of articles such as collapsible tubes and bottle closures. The article is in- [52] U.S. Cl. 72/56 serted in a forming chamber having a die surface and [51] Int. Cl B21d 26/08 a combustible gaseous mixture is ignited. The prod- [58] Field of Search 72/56; 29/421 E; 425/1 ucts of combustion result in increased pressure within the forming chamber to produce expansion of the arti- [56] References Cited cle against the die surface.

UNITED STATES PATENTS 3.195.334 7/1965 Filler 72/56 10 l Drawmg F'gure US. Patent Sept. 30,1975

HIGH ENERGY FORMING The present invention relates to the shaping of articles, typically collapsible tubes, bottle closures and the like.

It has, for instance, been proposed to manufacture collapsible tubes having a shaped, decreasing crosssection towards a dispensing end, the arrangement being such that the tubes, prior to filling, may be nested one within the other to facilitate transport and to aid handling on a filling line. Tubes of this general type are usually formed by the extrusion of a blank of material to form a cylindrical walled collapsible tube the wall of which is thereafter expanded or shaped in a desired manner, usually as a frusto-cone.

The expansion of tubes to frusto-conical form is usually effected using an expanding mandrel comprising a plurality of segments which together define a substantially cylindrical surface over which the tube to be expanded is located. The segments are adapted to hinge about a forward end disposed towards the dispensing opening of the tube while the rearward portion of thesegments are caused to expand thereby defining a substantially frusto-conical taper surface. On collapsing of the mandrel, the mandrel is withdrawn from the tube to leave the expanded tube ready for decorating and subsequent nesting to provide a stick of frusto-conical shaped collapsible tubes.

The technique of expanding the tubes on an expanding mandrel meets many of the requirements of an automated industrial process but the stretching of the tubes themselves during expansion is not uniform over the surface thereof and unless the annealing of the tube is carried out with precision, cracks and deformities can occur within the material of the tube walls which later causes the tube to fail with a consequent leakage of the contents from the tube.

According to the present invention, therefore, there is provided a method of shaping articles which method comprises placing an article to be shaped in a forming .chamber including a die surface defining the desired shape of the finished article, introducing a combustible mixture into the chamber, igniting said mixture and causing or allowing the products of combustion to ex- The present invention also includes shaped articles such as tubes and closures when made by the process of the invention. The present invention also includes apparatus for expanding an article, which apparatus comprises a forming chamber, the walls of which define 'the configuration of the expanded article, said chamber being adapted to accommodate said article, supply means for supplying a combustible fuel/air-or fuel/oxygen mixture to the vicinity of said tube, and ignition means for igniting said mixture to form products of combustion and to increase the pressure interiorly of the article to expand the same so that the walls of the expanded article lie contiguous the walls of the said chamber. The article entered into'the forming chamber prior to expansion may be a cylindrical collapsible tube v and the walls of the forming chamber may define a frusto-conical cavity. Additional flares and expansions may be provided in the wall of the forming chamber constituting the die surface in order that various shapes and patterns may be applied to the form of the shaped and expanded tube. I

The combustible mixture may be a mixture of any well known combustant and air typical mixtures being provided by petrol/air mixtures, natural gas/air mix-" tures, hydrocarbon/air mixtures and coal gas/air mixtures. The fuel may be supplied as a gas or vapour to a combustion chamber juxtaposed said article whereby on ignition, the gases generated by the explosion are caused to debouch from the combustion chamber to the interior of the article, the expanding gases causing the article to expand against said die surface, after which they are exhausted into the atmosphere.

The supply means for supplying the products of combustion to the article may comprise a combustion chamber accommodating an inlet valve for the admission of a combustible mixture to the chamber and ignition means for igniting the mixture. The combustion chamber may also include heater means for heating the combustible mixture prior to ignition. The combustion chamber may be provided with an outlet communicating with a valve chest accommodating valve means adapted to open under the increase in pressure of the combustion products to allow said combustion products to pass from the'combustion chamber into the valve chest. The valve chest may be adapted to communicate with the article forming chamber, and the said article may be disposed within said chamber with the open end of the article engaging a sealing element so that the expanding gases pass via said sealing element into said article whereby on expansion of the tube, the open end of the article is expanded away from the seal element thereby allowing the exhaust gases from the combustion chamber to pass via said tube interior to exhaust portsleading to the atmosphere.

The method and apparatus described above produces rapid expansion of the articles substantially uniformly over the collapsible walls thereof, thereby decreasing the magnitude of the discontinuities produced within the wall structure itself and providing an article less likely to rupture during service.

The nature of the'combustion is not an explosion but a flashover. The pressures generated by the combusthe temperature which will prevail, and hence the pressures shouldbe limited below the level at which the temperatures approach the melting point of the tube material. In practice, the pressure of the combustion products may be limited .by the economics of supplying fuel and air or oxygen under pressure to obtain optimum tube quality commensurate with cost of production. a

Following is a description by way of example only and with reference to the accompanying drawing of one method of carrying the invention into effect. .In the accompanying drawing the FIGURE is a diagrammatic cross-section through apparatus for expanding tubes in accordance with the present invention.

The apparatus comprises a cylindrical combustion chamber 11 disposed, in the accompanying drawing, with its axis substantially horizontal. The-rearward end 12 of combustion chamber 1 1 is closed by cap 13 comprising a disc portion 14 with a forwardly extending cycombustion chamber 11. The cap 13 also carries an inlet valve 21 disposed radially with respect to heater 17 in a position substantially intermediate the longitudinal axis of combustion chamber 11 and the inner surface of the cylindrical wall of said chamber 11. The inlet valve' debouches' into plenum chamber22 which communicates with helical tube 18 by means of interconnecting tube 23 formed integral therewith so that in operation a combustible gaseous mixture can be supplied via inlet valve 21 through plenum chamber 22 to helical conduit 18. The end cap 13 further accommodates (in the diameter containing valve 21, an igniter 24 constituted by an automobile sparking plug, the igniter 24 being disposed on the side of heater l7 opposite to valve 21. I

The forward end of the combustion chamber carries a second closure cap 25 having a rearwardly extending cylindrical skirt 70 which is similarly screw threaded by means of thread 71 to the forward end of chamber 11. The forward closure cap 25 has a central bore 26 adapted to debouch into a substantially cylindrical valve chest 27. The valve chest 27 has a cylindrical compartment 28 and the rearward end of valve chest 27 has an'inwardly projecting annular flange constituting a valve seat 29 of generally fr'usto-conical form extending from the forward extremity of the cylindrical bore in cap 25. The valve chest 27 is provided towards itsforward end with a support 30 of substantial thickness, said support 30 having a central bore '31 which ac commodates a stem 32 of 'a poppet valve 33 having a disc-like head 34 adapted to engage with valve seat 29, the arrangement being such that the cylindrical valve chest 27, the stem 32 and the disc-like valve head 34 are substantially coaxial with the longitudinal axis of combustion chamber 11. The valve stem 32 extends forwardly of the cylindrical valve chest 27. The poppet valve 33-. is "spring loaded by means of compression spring 35 rearwardly of support 30 so that the valve head 34 engages seat 29. The support 30 is provided with a plurality of expansion ports 36 for the passage of gases in a forward direction. The valve chest 27 carries at its forward end a forwardly extending cylindricalportion 43 having a central bore 45 capable ofaccommodating the stem 32 of valve 33 when the valve head 34 is withdrawn forwardly from its datum position abutting seat 29. The cylindrical portion 43 has at its forward end a frusto-conical seal element 44. The valve chest 27 is releaseably connected, by means of a quick release mechanism (not shown) with a tube forming chamber comprising a substantially cylindrical body portion 51 having a frusto-conical cavity 52 extending from its rearward end 53 and tapering towards its forward end 54. The. forward end is closed by a head piece 55 a central portion of which defines the forward extremity of chamber 52 and is contoured and recessed at 56 to accommodate the shoulder and closure portion of a collapsible tube. The forming chamber is arranged toextend to encompass the tube seal element 44 in the end of the tube forming chamber of maximum dimension. The tube-forming chamber also has a plurality of radial exhaust ports 57 towards its rearward end the arrangement being such that gases introduced into the forming chamber via conduit 45 'may, after expansion ofany tube disposed therein, pass rearwardly about 'seal 44 to be exhausted from the chamber by means of exhaust ports 57.

In operation, a collapsible tube 60, having cylindrical walls, is disposed within the forming chamber with its open end 61 engagingseal 44 and the closure of the tube being accommodated within the recess 56 in the head piece 55 of the tube forming chamber. A combus tible gaseous mixture, typically natural gas and air, is introduced into the combustion chamber ll'via inlet valve 21 to pass into plenum chamber 22 and into helical conduit 18 where the gaseous mixture is heated by means of heater 17. The gaseous mixture debouches from the helical tube 18 by means of inlets 19 into chamber 11. A spark'is then generated by igniter or spark plug 24 to propagate a combustion within the combustion chamber.

As the combustion of the gaseous mixture in chamber 11 takes place, the gases in the combustion chamber expand rapidly to drive valve head 34 forwardly against the rearward spring loading of spring 35 to allow gases to pass suddenly and at high velocity from combustion chamber 11 via valve chest 27 and through conduit 45 extending forwardly of valve chest 27 and interiorly of tube 60. The increased pressure causes the walls of the tube 60 to expand outwardly and rapidly to conform with the frusto-conical shape of the interior surface 52 of the forming chamber 51, the expansion unseating the rearward open end 61 of tube 60 from the tube seal'44 thereby permitting the exhaust gases to pass between the rearward end 61 and the tube seal 44 to the exhaust ports 57 for exhaust of the gases to the atmosphere. v

The production of tubes in the method described above has been found to result in a more rapid produc' tion rate for the tubes and the tubes thus'produced have been found to provide improved resistance to cracking on ageing. In addition, it has been found to-be possible to expand larger tubes than has hitherto been possible using an expanding mandrel.

I claim: 7

1. A method of shaping articles which method comprises placing an article to be shaped in a forming chamber including a die surface of the desired shape,v

introducing a combustible mixture into a combustion chamber, igniting said mixture within said combustion chamber, confining the products of combustion within said chamber until a predetermined threshold pressure the combustion chamber juxtaposed said article,

whereby on ignition, the gases generated by combustion are caused to debouch from the combustion chamber interiorly of the article to expand the article against the die surface. y

3. A method as claimed in claim 2 wherein the combustion mixture is heated prior to ignition.

4. A method as claimed in claim 1, the further step of positioning the article having an open end portion on a seal and causing the products of combustion, subsequent to expansion of the article, to be emitted from ber on ignition of the mixture within the combustion chamber the pressure generated therein operates said valve means to cause combustion products to enter the forming chamber to expand at least a portion of the article against said die surface.

6. Apparatus as claimed in claim 5 wherein a combustion chamber has an inlet valve for the admission of a combustion mixture to the chamber and ignition means for igniting the mixture.

7. Apparatus as claimed in claim 6 wherein the combustion chamber further includes heating means for heating the combustible mixture prior to ignition.

8. Apparatus as claimed in claim 7 wherein the combustion chamber is interconnected to the forming chamber via valve means adapted to open under the influence of an increase in pressure to the combustion products to allow the combustion products to pass from the combustion chamber to the forming chamber.

9. Apparatus as claimed in claim 7 characterized in that the forming chamber includes asealing element for sealing with an open end of a hollow article.

10. In an apparatus for shaping a hollow article to a predetermined final configuration the combination comprising: a forming chamber includinga die surface and opposite end portions, one said portion arranged to receive a part of the article to be shaped and the other said portion arranged to support an open end of said article, said forming chamber also including exhaust ports adjacent to said other portion and a secondary ignition chamber in axial alignment with said forming chamber including overload valve means capable of being reciprocated from an inoperative closed position to an instantaneous open position upon explosion of a combustible mixture in said ignition chamber to thereby unseat said valve means to allow entry of the products of combustion resulting from the explosion into the article to thereby expand the same. 

1. A method of shaping articles which method comprises placing an article to be shaped in a forming chamber including a die surface of the desired shape, introducing a combustible mixture into a combustion chamber, igniting said mixture within said combustion chamber, confining the products of combustion within said chamber until a predetermined threshold pressure is reached, and then allowing the products of combustion to pass into the forming chamber to expand the article against the die surface.
 2. A method as claimed in claim 1 wherein the article is a hollow article and wherein the fuel is supplied to the combustion chamber juxtaposed said article whereby on ignition, the gases generated by combustion are caused to debouch from the combustion chamber interiorly of the article to expand the article against the die surface.
 3. A method as claimed in claim 2 wherein the combustion mixture is heated prior to ignition.
 4. A method as claimed in claim 1, the further step of positioning the article having an open end portion on a seal and causing the products of combustion, subsequent to expansion of the article, to be emitted from said open end to exhaust.
 5. Apparatus for shaping a hollow article which apparatus comprises a forming chamber including a die surface, a combustion chamber juxtaposed said forming chamber, mixture supply means for the supply of a combustible mixture to the said combustion chamber, ignition means for igniting the mixture within said combustion chamber to form products of combustion, and valve means juxtaposed an inlet for said forming chamber on ignition of the mixture within the combustion chamber the pressure generated therein operates said valve means to cause combustion products to enter the forming chamber to expand at least a portion of the article against said die surface.
 6. Apparatus as claimed in claim 5 wherein a combustion chamber has an inlet valve for the admission of a combustion mixture to the chamber and ignition means for igniting the mixture.
 7. Apparatus as claimed in claim 6 wherein the combustion chamber further includes heating means for heating the combustible mixture prior to ignition.
 8. Apparatus as claimed in claim 7 wherEin the combustion chamber is interconnected to the forming chamber via valve means adapted to open under the influence of an increase in pressure to the combustion products to allow the combustion products to pass from the combustion chamber to the forming chamber.
 9. Apparatus as claimed in claim 7 characterized in that the forming chamber includes a sealing element for sealing with an open end of a hollow article.
 10. In an apparatus for shaping a hollow article to a predetermined final configuration the combination comprising: a forming chamber including a die surface and opposite end portions, one said portion arranged to receive a part of the article to be shaped and the other said portion arranged to support an open end of said article, said forming chamber also including exhaust ports adjacent to said other portion and a secondary ignition chamber in axial alignment with said forming chamber including overload valve means capable of being reciprocated from an inoperative closed position to an instantaneous open position upon explosion of a combustible mixture in said ignition chamber to thereby unseat said valve means to allow entry of the products of combustion resulting from the explosion into the article to thereby expand the same. 